The present invention relates to the use of selected surface-active substances, alone or in combination, for use in cleaning agents and in particular in dishwashing agents for automatic dishwashing.
The cleaning of hard surfaces and in particular the washing of dishes places particular requirements on the cleaners used. This is true especially for machine dishwashing. The three components of the machine system are cleaner, rinse aid and regenerating salt for softening the water. Here, the central tasks of the cleaner main constituent are soil release, soil dispersion, the binding of residual water hardness and corrosion inhibition. An important parameter for dishwashing is the clear-rinse performance. Here, it is ascertained how large the fraction of deposits on the ware parts is after these have been rinsed. The deposits are essentially mineral compounds, in particular Ca and/or Mg salts, but also surfactant residues. Primarily, however, lime leads to the deposits undesired for the user. In order to reduce the fraction of these deposits, customary dishwashing agents, especially those for automatic dishwashing, generally comprise so-called rinse aids. Standard commercial rinse aids are usually mixtures of weakly foaming nonionic surfactants, typically fatty alcohol polyethylene/polypropylene glycol ethers, solubility promoters (e.g. cumene sulfonate), organic acids (e.g. citric acid) and solvents (e.g. ethanol). The aim of these agents is to influence the interfacial tension of the water in such a way that it can run off the ware in the thinnest possible coherent film such that no water drops, streaks or films are left behind during the subsequent drying operation. A distinction is made between two types of deposits. Firstly, the so-called “spotting” is investigated, which arises as a result of drying water drops, and secondly “filming” is evaluated, i.e. layers which are formed by the drying of thin water films. For the evaluation, test persons are currently used who visually evaluate the parameters of “spotting” and “filming” on cleaned objects, e.g. plates, glasses, knives etc. Modern cleaning agents for dishwashing therefore comprise rinse aids in order to improve the run-off of water from the surfaces of the ware. There are rinse aids which do not dry equally as well on all substrates, such as e.g. plastic. In order to avoid this effect, complex classic rinse aids are formulated, which have e.g. silicone compounds and/or fluorinated compounds, as are described in U.S. Pat. No. 5,880,089 or US 2005/0143280 A1. However, these compounds are biodegradable with difficulty, if at all, and some are even hazardous to the environment.
More recently, combination products have increasingly been used; these combine the different functions, such as cleaning, clear rinsing, water softening and optionally metal protection, in particular silver protection, or a glass protection functions in a, preferably solid, supply form. Such agents are referred to as multifunctional agents. Thus, for example so-called 3-in-1 products which combine cleaner, rinse aid and water softener in the form of a solid compact (“tab”) are found on the market. As a result of the increased use of such multifunctional agents, however, the drying performance has become worse compared to using a classic rinse aid. Drying performance is to be understood here as meaning to what extent the cleaned ware still has water, preferably water drops, on the surface after passing through the dishwashing process. The water remaining on the surface then has to either be removed mechanically (e.g. by wiping dry) or the ware has to be left to dry in the air. The user thus has to wait until the water has evaporated. In this connection, however, residues (e.g. lime and/or surfactant residues or other residues which were dissolved or dispersed in the water) remain on the surface and lead to unesthetic marks or streaks. This is true to a particular extent on shiny or transparent surface, such as e.g. glass or metal. For this reason, ways have been sought to improve the drying performance of cleaning agents for hard surfaces, in particular of dishwashing agents. EP 1 306 423 A2 discloses aqueous cleaning agents which comprise alkyl ether sulfates and amphoteric glycine compounds and are suitable for improving the drying behavior of dishwashing agents. DE 100 45 289 A1 describes hand dishwashing agents which comprise certain quaternary ammonium compounds and alkyl ether sulfates alongside one another and likewise exhibit particularly good drying behavior.
Furthermore, additives for cleaning agents must not adversely affect the washing performance, and in particular the clear-rinse performance, of the cleaners. In an ideal case, an addition should even improve the performance of the cleaner overall.